Image capturing devices known in the related art include the image-capturing device disclosed in patent literature 1. The image-capturing device includes an image sensor disposed on a predetermined focal plane of a photographic lens (optical system). The image sensor has arrayed thereat focus detection pixels, each constituted with a micro-lens and a pair of photoelectric conversion units disposed to the rear of the micro-lens. A pair of image signals corresponding to a pair of images formed with a pair of focus detection light fluxes passing through the optical system are generated as analog signals via the pair of photoelectric conversion units. The pair of analog signals are read out from the image sensor independently of each other and the focusing condition (defocus amount) at the photographic lens is detected by detecting an image shift amount (phase difference) indicating the extent of image shift manifested by the pair of image signals. Image information is generated as the analog signals, generated at the pair of photoelectric conversion units in each focus detection pixel, are analogously added together within the focus detection pixel and the analog signal resulting from the addition is read out as an image signal from the image sensor.